The present invention relates to the field of communications, and more particularly, to a network of mobile communication systems operating with directional antennas.
Time division multiple access (TDMA) is one example of an access scheme used for establishing communication links between wireless mobile communication systems. Communication links between the wireless mobile communication systems are established within a series of time frames. Each time frame is divided into time slots, with each wireless mobile communication system being assigned at least one time slot.
An omni-directional antenna is typically used by a wireless mobile communication system so that information transmitted by one mobile communication system is received by all the other mobile communication systems. When the mobile communication systems are operating at a fixed frequency, they must take turns transmitting within their respective time slots to prevent channel interference.
To improve quality of a communications link between two wireless communication systems, a directional antenna may be used. The directional antenna provides an increased antenna gain in a desired area that is limited in coverage while decreasing the antenna gain towards the remaining area.
U.S. Pat. No. 5,767,807 to Pritchett discloses phased array antennas being used for establishing communication links within a network of wireless communication systems. The phased array antenna includes parasitic elements for selectively controlling the antenna pattern. The phased array antenna radiates an omni-directional signal when all of the parasitic elements are in a high impedance state, and radiates a directional signal when a selected number of parasitic elements are placed in a lower impedance state in response to switching circuits.
More particularly, the Pritchett ""807 patent discloses the acquisition, by a fixed initiating wireless communication system from a fixed receiving wireless communication system, of a list of the wireless communication systems operating in the network and a corresponding respective time slot list for each wireless communication system. A table is then created based upon the list for scheduling time slots among the wireless communication systems.
Scheduling time slots for wireless communication systems operating with directional antennas, particularly when the wireless communication systems are mobile, is complex. In such a dynamic network, mobile communication systems are continuously entering into and dropping out of the network. Furthermore, Parallel operations may be desired to reduce time slot allocation delay.
It is an object of the present invention to schedule time slots and reduce time slot allocation delay in communication link demands in a wireless mobile ad hoc network.
This and other objects, advantages and features in accordance with the present invention are provided by a wireless communication network including a plurality of mobile nodes each having a transceiver, a directional antenna, e.g. a phased array antenna, connected to the transceiver, and a controller connected to the transceiver. The controller includes a time slot unit to initiate at least one semi-permanent time slot request for respective time frames to establish a communication link with each neighboring mobile node and leaving at least one available time slot in each time frame, while processing multiple received semi-permanent time slot requests from neighboring mobile nodes. A second time slot unit initiates at least one available time slot request to also serve the communication link with a neighboring mobile node based upon link communications demand, while processing multiple received available time slot requests from neighboring mobile nodes. An antenna aiming unit aims the directional antenna toward each neighboring mobile node during communication therewith.
The controller may temporarily allocate a particular time slot to a plurality of neighboring mobile nodes but selects only one of the plurality of neighboring nodes for the particular time slot. The first time slot unit may initiate a plurality of semi-permanent time slot requests for respective time frames. Each communication link is formed by an initiating mobile node and a receiving mobile node, and the initiating mobile node transmits a list of available semi-permanent time slots to the receiving mobile node. The receiving mobile node transmits selection of one of the semi-permanent time slots to the initiating mobile node. Here, the initiating mobile node confirms selection of the selected semi-permanent time slot to the receiving mobile node.
Objects, advantages and features in accordance with the present invention are also provided by a method for establishing communication links for the plurality of mobile nodes. The method includes initiating at least one semi-permanent time slot request for respective time frames to establish a communication link with each neighboring mobile node and leaving at least one available time slot in each time frame, while processing multiple received semi-permanent time slot requests from neighboring mobile nodes, and initiating at least one available time slot request to also serve the communication link with a neighboring mobile node based upon link communications demand, while processing multiple received available time slot requests from neighboring mobile nodes. The directional antenna is aimed toward each neighboring mobile node during communication therewith.